1. Field of the Invention
The present invention relates to a method and an apparatus for communicating in a wireless communication system. More particularly, the present invention relates to a method and apparatus for uplink power control in a wireless communication system.
2. Description of the Related Art
Recently, with the increasing demand for data communication and the continuing development of various communication services in a wireless communication system, there is an urgent need to increase transmission capacity. As a way to satisfy this need for an increase in transmission capacity, technology for heterogeneous networks is being actively studied. A heterogeneous network refers to a communication system in which cells with various phases, cell coverage, and characteristics are mixed and operated.
Hereinafter, a configuration of a related heterogeneous network will be described with reference to FIG. 1.
FIG. 1 illustrates an example of a related heterogeneous network.
Referring to FIG. 1, a heterogeneous network includes a system in which a macro cell 100 and at least one small cell (e.g., pico cells 102, 104, 106) with different-sized cell coverage are overlaid and operated. Although not shown in FIG. 1, the small cell in the cellular network 100 of the macro cell may include a femto cell, a pico cell, and/or the like.
In the heterogeneous network, the transmission capacity of the overall system can be increased by reusing transmission resources of the small cells (e.g., the pico cells 102, 104, 106, a femto cell, or the like) included in the macro cell 100. For example, when one small cell with a transmission band of 10 MHz is included in the macro cell 100 in which a transmission band of 10 MHz is used, a transmission band of 20 MHz in total is available in the macro cell 100. That is, when N small cells are included in one macro cell, a transmission band that is N times as large as an existing transmission band is available in the macro cell, and thus a transmission rate can be increased by N times.
However, in the actual wireless communication environment, there is a problem in that even when N small cells are included in one macro cell, a transmission rate corresponding to N times of an existing transmission rate cannot be obtained and smaller transmission gain is achieved due to interference between heterogeneous cells and non-uniform distribution of mobile terminals. That is, in a related heterogeneous network system, performance degradation may be caused by interference between a macro cell and a small cell, or by interference between small cells. Also, in a related heterogeneous network system, non-uniform distribution of mobile terminals with respect to small cells may cause some resources to be unusable, thereby resulting in performance degradation of the related heterogeneous network system.
Active research has recently been conducted on a network coordinate system employing a centralized control scheme, which uses direct connection links between cells inside and outside a heterogeneous network. The network coordinate system employing a centralized control scheme allows various individual cells included in a wireless communication system to analyze mutual influences between corresponding cells and the associated effects of such influences to collaboratively perform wireless transmission and reception operations. Therefore, in the network coordinate system employing a centralized control scheme, mutual influences between cells can be minimized, and system efficiency can be maximized.
Hereinafter, a related network coordinate system employing a centralized control scheme will be discussed with reference to FIG. 2.
FIG. 2 illustrates an example of a related network coordinate system employing a centralized control scheme.
Referring to FIG. 2, the network coordinate system employing a centralized control scheme includes a central controller 200 for generally controlling cells connected thereto through links or cells connected thereto through a specific network, a macro base station 210 for servicing a wide area or central region, and small cell base stations 220, 230, and 240, each for servicing a narrow area or partial region. For example, each of the small cell base stations 220, 230, and 240 may be a Distributed Antenna System (DAS) cell base station, or relay station.
The macro base station 210 and the small cell base stations 220, 230, and 240 are connected to each other through the central controller 200 and the links. Also, the macro base station 210 and the small cell base stations 220, 230, 240 connected to the central controller 200 can share information with each other. Thus, the macro base station 210 and the small cell base stations 220, 230, and 240 can collaboratively control transmission power or regulate interference. However, a method for controlling power using the above-mentioned centralized control scheme has not been concretely designed. As a result, communication systems must use an existing inefficient power control method in the related network coordinate system employing a centralized control scheme, which results in performance degradation of the related network coordinate system.
Therefore, a need exists for a method and apparatus for effectively controlling the power in a network coordinate system employing a centralized control scheme.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.